مقدمه انگلیسی

Preference-based health-related quality of life
(HRQoL) instruments, including the EQ-5D [1],
Health Utilities Index [2] and the SF-6D (derived from
the SF-36) [3] summarize HRQoL in a single index
score and are used in cost-utility analyses with the aim
of informing clinical policy and resource allocation
in health care [4]. Each preference-based HRQoL
instrument typically comprises a health classification
system for describing the respondent in terms of a
health state (HS), and a utility function that maps each
HS to a utility score. The utility function is typically
derived from a population-based HS valuation study in
which respondents express their preferences for individual
HS. These values are then aggregated using
statistical modeling techniques to derive the utility
function [5,6].
A variety of valuation methods have been employed
in eliciting HS preferences, with choice-based valuation
methods clearly preferred [7]. Standard gamble
(SG) and time trade-off (TTO) are two choice-based
methods with demonstrated acceptability, reliability,
and validity in Western sociocultural contexts [7,8].
Both SG and TTO have established theoretical underpinnings
[9,10], with the former being frequently
referred to as the “gold standard” because it is directly
based on the axioms of expected utility theory [9]
although the latter requires the additional assumptionthat utility in additional healthy time is linear with
respect to time [11]. Nevertheless, TTO is preferred by
some (though not by others [12]) for its ease of implementation
[9,10]. Importantly, studies have shown
that health utilities elicited by both methods are
usually different, with SG typically generating higher
scores [13,14]. Hence, in planning studies to use
choice-based preference measures such as SG and TTO
in settings in which there has been relatively little
experience with these measures, it is important to
obtain empiric evidence with regard to validity, feasibility,
and acceptability of each of these methods.
Existing studies comparing SG and TTO have
largely taken a quantitative approach [7,13,15], with
no studies (to the best of our knowledge) having
addressed qualitative aspects to better understand
individual subject’s preferences and behavior when
completing these exercises. We therefore conducted
such a study in a multiethnic Asian population, in
which a diversity of views might be expected. In this
study, which is likely to be the first head-to-head
comparison of SG and TTO methods in an Asian
population, we aimed to assess the validity, feasibility
and acceptability of SG and TTO and to evaluate
if systematic differences in SG and TTO scores
observed in other studies [13,14] were also observed
in this Asian population. We defined 1) acceptability
as the degree to which subjects are satisfied with SG
and TTO and have no objections to these methods;
and 2) feasibility as the extent to which SG or TTO
exercise may be done practically and successfully. We
then aimed to move beyond descriptive statistics (e.g.,
completion rate and missing data) to gain an insight
into factors influencing individuals’ preferences for
SG or TTO.

نتیجه گیری انگلیسی

In this study among Chinese, Malay, and Indian Singaporeans
of various ages and educational levels, we
found that both SG and TTO were valid, feasible, and
acceptable for eliciting health preferences in this population.
Nevertheless, there were systematic differences
in utility scores elicited by both methods. We also
evaluated factors influencing individuals’ preferences
for SG or TTO methods. In multivariable analysis with
adjustment for ethnicity, age (per 10 years), gender, and
education, older age was only marginally associated
with preference for TTO over SG. Hence, our results
suggest that both SG and TTO may be used among
subjects of genders, various ages, ethnicities, and education
levels in population-based HS valuation studies
to be conducted in this population. To the best of our
knowledge, this is the first such study among Asians,
and provides a useful framework for comparison with
future studies in other Asian sociocultural contexts.
Several aspects of our findings deserve comment.
First, consistent with other published studies [18,19],
we found that agreement between SG and TTO utility
scores was generally poor, with SG scores being generally
higher than TTO scores. It was interesting that
the lack of agreement was consistently evident in the
three HS studied (a mild, moderate, and severe state
of health). Second, although the feasibility of SG in
population-based study had previously been questioned
[20], our results suggest that SG may be as
feasible as TTO method in such a setting, given that
our subjects preferred SG as much as, if not more than,
TTO (except for older subjects who marginally preferred
TTO to SG). Third, although subjects rated
both SG and TTO instructions as easy to understand,
there were 10 subjects who felt TTO instructions could
be revised to improve clarity and reduce offensiveness,
a finding consistent with the trend (not reaching statistical
significance) that more subjects preferred SG.
That nine of these subjects were Malay suggested that
TTO instructions could be particularly difficult for
this ethnic group (although the differences in ratings
among ethnic groups were not statistically significant).
As there were almost equal numbers of these subjects
who completed the English (n = 4) and Malay (n = 5)
language versions, the difficulty is unlikely to be due to
translation. Fourth, open discussion of death has been
thought to be taboo among Asians [21,22], with many
avoiding this topic because of the perception of bringing
“bad luck” on oneself by discussing death, even if
it is just speaking the words with the same phoneme as
the word for death [23]. Nevertheless, it was interesting
and encouraging that our subjects were comfortable
with discussing death.
The results of this study have several implications,
some of which would have a bearing on future
research. First, to date, this is the only published study
in Asia that concurrently evaluated both SG and TTO
methods for eliciting health preferences. Our results
suggest that both methods are valid, feasible, and
acceptable and may be used in future clinical trials for direct measurement of health utility scores in this
population. Second, the semiquantitative nature of
this study provided glimpses of the decision making
process of subjects completing such studies, which
would be useful in explaining differences in preferences
for the same HS. For example, we found that religious
beliefs may influence an individual’s health preferences
in that giving up life years is not an option for some
individuals. Given that 7.9% of the Singaporean population
are Indians and 13.9% are Malays [24] and that
4.8% of Indian and 10% of Malay subjects in this
study felt that discussing trading off life years was
offensive for religious reasons, we estimated that up to
1.8% of the Singaporean population may find that
discussing trading off life years was offensive because
of their religious beliefs. Thus, these individuals are
unlikely to say, “I would rather die immediately than
be confined to bed,” and would thus assign higher
preference scores to the HS of being confined to bed
than those whose religious beliefs did not inhibit
trading quantity for quality of life. Nevertheless, the
extent of the influence of religiosity on actual SG and
TTO scores remains to be evaluated in future studies.
This is because in a local study that measured health
preferences for HUI3 HS among Chinese, Malays, and
Indians using the SG [25], there were no ethnic differences
in health preferences for these HS. Nevertheless,
the study did not include any measures of religiosity.
We recognize several limitations of this study. First,
the study sample was not drawn at random from the
Singapore population, which was not feasible because
of cost and logistic issues. We therefore attempted to
improve representativeness by specifying criteria to
ensure equal gender and ethnic representation with a
wide age range. Second, to reduce respondent burden,
we asked subjects to evaluate only three HS each for
SG and TTO, although the number of HS to be valued
in existing valuation protocols typically exceeds three
[26,27]. Hence, generalizability of our findings to HS
valuation studies involving more than three HS needs
confirmation. Third, we have used simple VASs to
measure risk attitudes as no other suitable measures
were available for this population at the time of this
study. The association (or the lack of it as found in this
study) between risk attitudes and preference for SG or
TTO methods in this population could thus be further
studied when better measures for assessing risk attitudes
become available.
In conclusion, this study found both SG and TTO
methods to be valid, feasible, and acceptable among
Chinese, Malays, and Indians of various sociodemographic
backgrounds. The findings are therefore likely
to be applicable for population-based HS valuation
studies in this multiethnic Asian population. Nevertheless,
generalizability of our study findings needs to be
confirmed in larger studies surveying subjects who are
representative of the population being studied.
We would like to thank Mdm. Halimah Beevi and Ms.
Syzawani Bte Amrun for their assistance in conducting the
interviews.
Conflict of Interest: It should be noted that David Feeny
has a proprietary interest in Health Utilities Incorporated,
Dundas, Ontario, Canada. HUInc. Distributes copyrighted
Health Utilities Index (HUI) materials and provides methodological
advice on the use of HUI.